The present invention relates to a mount structure for an engine accessory, and more particularly to a mount structure for an engine accessory which improves stiffness of a mount for an accessory without increasing the weight of the engine.
Generally, various kinds of accessories are provided for keeping up and improving the performance of the engine. Each accessory is mounted on the engine block at an appropriate position in accordance with its purpose. For example, when a rotation driving force is required to drive an accessory, the accessory is mounted on the engine at the timing belt side in such a manner that the accessory is wound around by the timing belt or a belt for driving other accessories. If the accessory does not require a rotation driving force and is provided for the control purpose, the accessory is mounted at a position adjacent to the controlled object in accordance with its function. For example, an EGR valve for controlling the flow rate of recirculation flow of exhaust gas flowing to the intake side or a spool valve such as disclosed in Japanese Laid-open Patent Application No. 2000-240743 for switching hydraulic pressure to drive a variable valve timing mechanism is mounted at one side of the cylinder head positioned upward of the engine.
When various kinds of accessories are mounted on the engine, a necessary and sufficient stiffness is required for each mount in order to prevent damage around the joint of the mount portion or malfunction of the accessory by a vibratory force due to vibration of the engine. Particularly, in the case of an accessory for feeding hydraulic pressure to the cylinder head, a sufficient stiffness is required at the mount portion because of the necessity to ensure a good sealing performance to prevent leakage of hydraulic fluid from the joint surface.
However, in the case that an accessory is mounted at the intake side of the cylinder head, if the mount portion is formed too thick in order to ensure a sufficient stiffness, the weight of the engine will increase disadvantageously.
Meanwhile, in the case that an accessory is mounted at the exhaust side of the cylinder head, the mount portion has to project to a certain extent away from the cylinder head such that the accessory is not subjected to excessive heat from the cylinder head. Such a mount structure will also increase the weight of the engine, leading to deterioration of the fuel economy and the like.
In order to eliminate the aforementioned drawbacks, the present invention seeks to provide a mount structure for an engine accessory which ensures the attachment of the engine accessories with high stiffness and with minimum increase in the weight of the engine.
According to a first aspect of the invention, there is provided a mount structure for an engine accessory. In a cylinder head of an engine having an intake port communicating with an combustion chamber of the engine, the mount structure comprises: an engine accessory; an accessory mount portion provided on the cylinder head and to which the engine accessory is mounted; and a fuel injection device mount portion provided on the cylinder head and to which a fuel injection device is mounted, the fuel injection device injecting fuel into the intake port; wherein the accessory mount portion is joined to the fuel injection device mount portion.
In this mount structure for an engine accessory, since the fuel injection device mount portion and the accessory mount portion are joined together, the accessory mount portion and the fuel injection device mount portion are reinforced with each other to provide high stiffness. Further, since the engine accessory is mounted at the intake side of the engine, the temperature of the accessory mount portion is lower than the case where the engine accessory is mounted at the exhaust side. Therefore, it is not necessary for the engine accessory to keep so much distance away from the cylinder head. This leads to improvement of stiffness without excessively increasing the thickness of the mount portion.
According to a second aspect of the invention, there is provided a mount structure for an engine accessory. In a cylinder head of an engine having an intake port communicating with an combustion chamber of the engine, the mount structure comprises: an engine accessory; an accessory mount portion provided on the cylinder head and to which the engine accessory is mounted; and a cooling water pipe mount portion provided on the cylinder head and to which a cooling water pipe is mounted, the cooling water pipe circulating therein cooling water for cooling the interior of the engine; wherein the accessory mount portion is joined to the cooling water pipe mount portion.
In this mount structure for an engine accessory, since the accessory mount portion and the cooling water pipe mount portion are reinforced with each other, stiffness of the accessory mount portion is improved. Further, since the engine accessory is mounted adjacently to the cooling water pipe mount portion, it is possible to restrict excessive increase in temperature around the accessory mount portion. Therefore, it is not necessary to project the accessory mount portion from the cylinder head, which reduces the entire size of the engine.
According to a third aspect of the invention, there is provided a mount structure for an engine accessory. In a cylinder head of an engine having an intake port communicating with an combustion chamber of the engine, the mount structure comprises: an engine accessory; an accessory mount portion provided on the cylinder head and to which the engine accessory is mounted; and an intake manifold mount portion provided on the cylinder head and to which an intake manifold is mounted, the intake manifold communicating with the intake port; wherein the accessory mount portion is joined to the intake manifold mount portion.
In this mount structure for an engine accessory, since the accessory mount portion and the intake manifold mount portion are reinforced with each other, stiffness of the accessory mount portion is improved. Further, since the engine accessory mount portion and the intake manifold mount portion are joined together, it is possible to restrict excessive increase in temperature around the accessory mount portion. Therefore, it is not necessary to project the accessory mount portion from the cylinder head, which reduces the entire size of the engine.
Preferably, in the aforementioned mount structures, the intake port is bent in such a manner that an upstream side of the intake port is away from the accessory mount portion.
In such a mount structure for an engine accessory, since the accessory mount portion is arranged near to the fuel injection device mount portion or the intake manifold mount portion, it is possible to provide the accessory mount portion on the cylinder head without projecting outward in the direction of the output shaft of the engine and without increasing the entire size of the engine. In other words, since the upstream of the intake port is bent in a direction away from the accessory mount portion, the accessory mount portion can be positioned toward the center part of the engine, thereby allowing the entire size of the engine to be downsized as well as permitting much more sufficient joint of the accessory mount portion to the fuel injection device mount portion or the intake manifold mount portion. This can provide a mount structure for an engine accessory having high stiffness without increasing the weight.
Further, it is preferable that an intake manifold mount surface of the intake manifold mount portion and an accessory mount surface of the accessory mount portion are formed in the same plane. In this mount structure for an engine accessory, since the intake manifold mount surface and the engine accessory mount surface are formed in the same plane, these two surfaces can be machined and finished simultaneously, thereby reducing the production cost.